CUMYL-4CN-BINACA Is an Efficacious and Potent Pro-Convulsant Synthetic Cannabinoid Receptor Agonist

Abstract

Synthetic cannabinoid receptor agonists (SCRAs) are the largest class of new psychoactive substances (NPS). New examples are detected constantly, and some are associated with a series of adverse effects, including seizures. CUMYL-4CN-BINACA (1-(4-cyanobutyl)-N-(2-phenylpropan-2-yl)indazole-3-carboxamide) is structurally related to potent, cumylamine-derived SCRAs such as 5F-CUMYL-PINACA, but is unusual due to a terminal aliphatic nitrile group not frequently encountered in SCRAs or pharmaceuticals. We report here that CUMYL-4CN-BINACA is a potent CB₁ receptor agonist (K _i = 2.6 nM; EC₅₀ = 0.58 nM) that produces pro-convulsant effects in mice at a lower dose than reported for any SCRA to date (0.3 mg/kg, i.p). Hypothermic and pro-convulsant effects in mice could be reduced or blocked, respectively, by pretreatment with CB₁ receptor antagonist SR141716, pointing to at least partial involvement of CB₁ receptors in vivo. Pretreatment with CB2 receptor antagonist AM-630 had no effect on pro-convulsant activity. The pro-convulsant properties and potency of CUMYL-4CN-BINACA may underpin the toxicity associated with this compound in humans.

Keywords: CUMYL; convulsant; new psychoactive substance; novel psychoactive substance; seizure; synthetic cannabinoid.

Figure 1

Molecular structures of CUMYL-4CN-BINACA (1), CUMYL-5F-PINACA (2), AM-2232 (3), and AM-2201 (4). Note that CUMYL-4CN-BINACA and AM-2232 are the nitrile analogues of CUMYL-5F-PINACA and AM-2201, respectively.

Figure 2

Representative traces of individual experiments illustrating the change in fluorescence in (A) AtT20-CB1 and (C) AtT20-CB2 cells following addition of CUMYL-4CN-BINACA (4CN) and CP 55,940, and concentration response curves for activation of (B) CB₁ and (D) CB₂ receptors by CUMYL-4CN-BINACA (4CN) and CP 55,940 in AtT20 cells. For representative traces, a drop in fluorescence represents an efflux of membrane potential sensitive dye from cells as they hyperpolarize. The data are presented as fluorescence normalized to the average of the fluorescence 30 s immediately prior to drug addiction. The effects of vehicle (DMSO) addition are illustrated, and have not been subtracted from the drug traces. For concentration response curves, the drug response is expressed as a proportion of that to CP 55,940, 1 µM. Data points represent the mean ± SEM of at least six independent experiments, and were fit to a four parameter logistic equation.

Figure 3

(A) Effect of CUMYL-4CN-BINACA on mouse core body temperature, where the dashed vertical line denotes time of intraperitoneal injection. *p < .05, ***p < .001 compared to vehicle, AUC over 3 h post CUMYL-4CN-BINACA injection. (B) Effect of 0.3 mg/kg CUMYL-4CN-BINACA on mouse core body temperature following pretreatment (30 min prior, first vertical dashed line) with vehicle or 30 mg/kg SR141716 (rimonabant; CB₁ receptor antagonist). *p < .05 compared to vehicle + CUMYL-4CN-BINACA, AUC over 3 h post CUMYL-4CN-BINACA injection. For both (A) and (B), each point represents the mean change in body temperature from vehicle baseline (± SEM) for four animals.

Figure 4

Seizure activity following an intraperitoneal injection of 0.3 mg/kg CUMYL-4CN-BINACA (4CN), pre-treated with vehicle, SR141716 (3 or 30 mg/kg), or AM-630 (3 mg/kg). Data are presented as (A) total Racine scores computed from weighted sums of each seizure behavior, which are presented individually in Table 2 . Generalized tonic-clonic seizures were quantified but not observed under any condition. Locomotor data are presented in panel (B). Bars represent mean ± SEM, with n = 5–6 per group; **p < .01, one-way ANOVA with Dunnett’s contrasts, comparing each condition to the vehicle + 0.3 mg/kg CUMYL-4CN-BINACA condition.